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SubjectRe: [PATCH 0/4] io-controller: Use names rather than major:minor
Chad Talbott wrote:
> This stack (which includes Gui's patch for per-device weights),
> changes the various blkio.* stats to use the disks' names (sda, sdb,
> etc.) rather than major:minor pairs when printing statistics.

Hi Chad,

I have the same concern with Vivek. We'v already exported device number
pair to user since 2.6.33, It's better to keep the original ABI.

> Additionally setting a per-device policy can be done via the disk's
> name.

To keep things simple, can we add new API in block layer to lookup
device name by device number as following.

+int blk_lookup_devname(dev_t devt, char *name)
+{
+ struct class_dev_iter iter;
+ struct device *dev;
+ struct gendisk *disk;
+
+ class_dev_iter_init(&iter, &block_class, NULL, &disk_type);
+ while ((dev = class_dev_iter_next(&iter))) {
+ if (dev->devt != devt)
+ continue;
+
+ disk = dev_to_disk(dev);
+
+ disk_name(disk, 0, name);
+
+ return 0;
+ }
+ class_dev_iter_exit(&iter);
+
+ return 1;
+}
+EXPORT_SYMBOL(blk_lookup_devname);
+

So we can keep dev_t in blkio layer, and export to user a device name by calling
this function. Also, we retrive device number by calling blk_lookup_devt().
This change might keep things much simple. Jens, do you have any thoughts?

Thanks,
Gui

>
> This has the side effect of fixing the "root cgroup shows no stats"
> problem that Ricky mentioned.
>
> Chad
>
> ---
>
> Chad Talbott (4):
> blkio_group key change: void * -> request_queue *
> Adds an RCU-protected pointer to request_queue that makes it easy to
> io-controller: Add a new interface "weight_device" for IO-Controller
> Use disk-names to set blkio.weight_device policy
>
>
> block/blk-cgroup.c | 224 +++++++++++++++++++++++++++++++++++++++++++++---
> block/blk-cgroup.h | 23 ++++-
> block/blk-sysfs.c | 4 +
> block/cfq-iosched.c | 27 ++----
> include/linux/blkdev.h | 6 +
> 5 files changed, 248 insertions(+), 36 deletions(-)
>
>
>
>



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